1. Field of the Invention
The present invention relates to a method for recycling a cathode ray tube bulb.
2. Description of the Related Art
As shown in FIG. 1, cathode ray tubes, such as for a color television, are primarily made of a glass panel 1 and a funnel 2. A neck 3 and an exhaust tube 4 are connected to each other at the tip of the funnel 2 on the opposite side to the panel 1. An anode button 6 for applying a high voltage to the dag coating described below is provided on the funnel 2. The inner surface of the glass panel 1 is coated with a fluorescent film, and the inner surface of the funnel 2 is coated with a dag coating having carbon black as the main component. A frit glass 5 is disposed between the sealing faces of the glass panel 1 and the funnel 2, and heated to ca. 450xc2x0 C., thus crystallizing the frit glass 5 and fritting the glass panel 1 and the funnel 2 together. Then, an electrode gun is sealed into the neck portion 3 of the funnel 2, the funnel is exhausted through the exhaust tube 4, and the electron gun is treated electrically, thus completing the color cathode ray tube.
The manufacturing costs for a bulb made of a glass panel 1 and a funnel 2 make up a large part of the total cost for manufacturing a color cathode ray tube. For that reason, it is important to collect and reuse the bulbs that have turned defective during the manufacturing process and the bulbs from products that have turned defective, in order to drive down the manufacturing cost of the color cathode ray tube.
In order to separate the glass panel from the funnel, the frit glass has to be dissolved. Conventionally, the flit glass is dissolved with nitric acid (see, for example, JP H01(1989)-194239A or JP H03(1991)-156830A). The concentration of the nitric acid is usually set to 10 to 15 wt %. Often, an ultrasonic wave generator is used in combination, so as to enhance the corrosion of the flit glass with the nitric acid.
However, since nitric acid is very harmful to the environment and the human body, it has to be handled with utmost care. Also, because of the high corrosivity of nitric acid, there is the danger that it corrodes the anode button of the funnel. When the anode button is corroded, the funnel cannot be reused. Furthermore, the corrosivity of the nitric acid is also a cause for expensive counter-measures against corrosion and maintenance fees for the various kinds of equipment, such as the ultrasonic wave generator.
In accordance with the present invention, a method for recycling a cathode ray tube bulb comprising a panel and a funnel fritted together with a frit glass includes a step of separating the panel and the funnel, wherein at least a portion of the frit glass is dissolved by a solution of an organic acid.
This method uses an organic acid solution instead of nitric acid, so that it solves the problems caused by the high corrosivity of nitric acid. With this method, harm to the environment and the human body can be decreased, the corrosion of the anode button can be suppressed, and the costs for equipment and maintenance can be reduced.
In this method, it is possible to enhance the dissolution of the frit glass by oscillations caused by ultrasonic waves, as in conventional methods, but it is also possible to spray or blow the organic acid solution to dissolve the frit glass. More specifically, it is preferable to arrange the cathode ray tube bulb such that the frit glass is immersed in the organic acid solution, and to blow the organic acid solution against the frit glass in the organic acid solution.